Neutron protection device

Abstract

The present invention relates to an upper neutron protection device for a nuclear reactor assembly. This device comprises at least one container partly filled with a neutron-absorbing product and maintained within a wall located in the upper part of the assembly by at least one spacing plate. Application to fast neutron reactors.

We claim: 
     
       1. In a nuclear reactor fuel assembly comprising a foot and an assembly body connected to the foot having an upper part and a lower part, an upper neutron protection device comprising: a wall of substantially hollow shape and having an inner face and an outer face, said wall being fixed to said assembly body at the upper part thereof,   at least one container comprising: a closed outer cylindrical envelope,   an inner cylindrical envelope placed within said outer cylindrical envelope and whose thickness is smaller than the thickness of the outer envelope,   a deformable tube located inside said inner cylindrical envelope and defining a space between said deformable tube and said inner cylindrical envelope, said space being incompletely filled with a product having a high neutron absorption cross-section, said at least one container being disposed within said wall and maintained by at least one spacing plate which is fixed to the inner face of the wall.     
     
     
       2. A device according to claim 1 wherein said at least one spacing plate has an outer edge, whereof at least part is substantially rectilinear and fixed to the inner face of the wall and an inner edge, whereof at least part matches the shape of the container. 
     
     
       3. A device according to claim 2, wherein the outer edge of said at least one spacing plate has an upper part and a lower part and has in its upper part a portion which is inclined from top to bottom towards the outside of the wall and a slot opening towards the outside of said wall and permitting the coupling of said device by a handling means. 
     
     
       4. A device according to claim 2, wherein the inner edge of said at least one spacing plate has an upper part and a lower part and has, in its upper part, a portion inclined from top to bottom towards the inside of the wall and a slot opening towards the inside of said wall and permitting the coupling of said device by a handling means. 
     
     
       5. A device according to claim 1 comprising a plurality of spacing plates which are joined to one another. 
     
     
       6. A device according to claim 1 wherein said at least one spacing plate has an anti-vibration system. 
     
     
       7. A device according to claim 6, wherein said anti-vibration system comprises at least one groove made in said at least one spacing plate. 
     
     
       8. A device according to claim 1 wherein said at least one spacing plate is fixed to said wall by means of nails having a head welded to said wall. 
     
     
       9. A device according to claim 1 wherein said at least one spacing plate is fixed to said wall by means of profiled wedges. 
     
     
       10. A device according to claim 1 wherein said at least one spacing plate is fixed to said wall by means of localized deformations of said wall penetrating slots made in said at least one spacing plate. 
     
     
       11. A device according to claim 1 wherein said at least one spacing plate is fixed to the wall by means of a flange fixed to said wall by welding.